1. FIELD OF THE INVENTION
The present invention relates to a lubricating oil, and more particularly to a lubricating oil comprising perfluoropolyether oil as a base oil.
2. DESCRIPTION OF THE PRIOT ART
Perfluoropolyether oil is used in maintenance-free locations under stringent application conditions over a long time owing to its distinguished heat resistance, chemical resistance and inertness to many materials. However, when perfluoropolyether oil is used under radioactive or energy irradiation conditions, for example, as a lubricating oil for pumps in a nuclear reactor, a corrosive hydrogen fluorine gas is generated as a decomposition reaction product at the radioactive or energy irradiation, different from a phenylether-based lubricating oil, etc., and is diffused not only into the lubricating oil, but also much more into the gas phase. Thus, it is impossible to use a perfluoropolyether-based lubricating oil under radioactive or energy irradiation conditions.
On the other hand, the phenylether-based lubricating oil resistant to the radioactive or energy irradiation is poor in other required properties such as low temperature application, temperature-viscosity characteristics, heat resistance, chemical stability, etc.